Devices for bone fixation using an intramedullary fixation implant

ABSTRACT

The invention comprises an intramedullary fixation implant and a method for joining bones and translating compression between the bones for treating various digital deformities. The intramedullary fixation implant comprises a first fixation portion and a second fixation portion connected to the first fixation portion, wherein the second fixation portion comprises a first projection and a second projection separated by a slot, and wherein the first projection and the second projection comprise a plurality of barbs shaped and arranged along the first and second projections such that they cooperatively form a thread along the second fixation portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 61/894,564, filed on Oct. 23, 2013, the entire contents of which areherein incorporated by reference. This application is also related toU.S. application Ser. No. ______, filed ______, entitled “Methods ForBone Fixation Using An Intramedullary Fixation Implant,” (AttorneyDocket No. 277-111B), the entire contents of which are hereinincorporated by reference.

FIELD OF THE INVENTION

This invention relates to the field of implant devices for bonefixation, and more particularly, to an intramedullary fixation implantused for the fixation of bones and the correction of deformities in thefoot or the hand, such as a hammertoe deformity.

BACKGROUND OF THE INVENTION

Digital deformities are among the most common forefoot pathologiesencountered by podiatrists and orthopedic surgeons. Digital deformitiesmay occur in the form of hammertoes, claw toes, mallet toes, bone spurs,overlapping and underlapping toes, mallet fingers, jersey fingers, andcoach's fingers, among others. The deformities typically affect theinterphalangeal joints of the hand or the foot, metatarsophalangealjoints of the foot, or metacarpophalangeal joint of the hand. Digitaldeformities in the fingers or toes result from imbalance of the tendons,causing them to stretch or tighten abnormally. These deformities may beeither congenial or acquired. For example, the deformities may be causeby neuromuscular and arthritic disorders, systemic diseases, flat orhigh-arched feet, or traumatic injuries to the joints. Toe deformitiescan also be aggravated by poorly fitting footwear.

Hammertoe, for example, results in a bend in the middle joint of the toeinto a claw-like deformity. While at first the patient may be able tomove and straighten the toe, overtime the hammertoe may become fixed. Inthis contracted position, the inside of the shoe rubs against thecontracted joints, causing corns to form on the top of the toe andcalluses to form on the sole of the foot. In certain patients thesecorns and calluses may open or ulcerate and form wounds. This causespain and discomfort in walking or wearing shoes. FIG. 1A depicts a humanfoot 100 afflicted with hammertoe deformity. Distal phalanx 101, middlephalanx 103, proximal phalanx 105, and metatarsal 107 bones are depictedin foot 100. The distal interphalangeal joint 104 is formed between thedistal 101 and middle 103 phalanges, proximal interphalangeal joint 106is formed between the middle 103 and proximal 105 phalanges, and themetatarsophalangeal joint 108 is formed between the proximal phalanx 105and the metatarsal 107. The hammertoe deformity in the foot is apparentin the proximal interphalangeal joint 106.

A similar digital deformity condition in the hand is depicted in FIG.1B. FIG. 1B depicts a human hand 110 afflicted with mallet fingerdeformity. Distal phalanx 111, middle phalanx 113, proximal phalanx 115,and metacarpal 117 bones are depicted in hand 110. The distalinterphalangeal joint 114 is formed between the distal 111 and middle113 phalanges, the proximal interphalangeal joint 116 is formed betweenthe middle 113 and proximal 115 phalanges, and the metacarpophalangealjoint 118 is formed between the proximal phalanx 115 and the metacarpal117. The mallet finger deformity in the hand is apparent in the distalinterphalangeal joint 114.

Early treatments for digital deformities include the use of strapping,taping, orthotics, or immobilization of the hand or the foot. However,once the deformity becomes fixed, surgical treatment will be necessary.Surgical treatments include bone fixation devices that fixate the bonesin order to fuse them into a stable mass. These orthopedic implantdevices realign bone segments and hold them together in compressionuntil healing occurs, resulting in a stable mass. Typical implantdevices include intramedullary nails, plates, rods and screws.

Infection and complications are a major concern in these procedures.Wound closure is technically demanding for the surgeon, and devices thatadd surface prominence, such as plates or exposed screws, add to thedifficulty by requiring greater tissue tension during incisionreapproximation. This increases the risk of post-operative woundinfections and dehiscence that may ultimately result in limb amputation.While there exist less intrusive devices, many devices lack theapplication of compression forces to the bone, causing the treated bonesto eventually become misaligned from the desired position.

There is therefore a need for improvements in intramedullary fixationimplants and methods of use that overcome some or all of the previouslydescribed drawbacks of prior fixation assemblies and processes.

SUMMARY OF THE INVENTION

The present invention is improved devices and methods for bone fixation.

The improved devices include an intramedullary fixation implant forjoining bones and translating compression between the bones for treatingvarious digital deformities. In a preferred embodiment, theintramedullary fixation implant comprises a first fixation portion and asecond fixation portion connected to the first fixation portion, whereinthe second fixation portion comprises a first projection and a secondprojection separated by a slot, wherein the first projection and thesecond projection comprise a plurality of barbs shaped and arrangedalong the first and second projections such that they cooperatively forma thread along the second fixation portion.

Broadly, the methods of the invention for joining and compressing afirst bone to a second bone of a joint comprise: creating a first holein the first bone, creating a second hole in the second bone, advancingthe first fixation portion of the intramedullary fixation implant intothe second hole in the second bone, counter-rotating the second bone,pressing the second fixation portion of the intramedullary fixationimplant linearly into the first hole in the first bone, and rotating thesecond bone into a final fixation position.

Instruments are also disclosed for use in practicing the invention.These include an implant driving tool for driving the first fixationportion into the second hole in the second bone.

Numerous variations may be practiced in the preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the invention can be obtained by reference toa preferred embodiment set forth in the illustrations of theaccompanying drawings. Although the illustrated embodiment is merelyexemplary of systems, methods, and apparati for carrying out theinvention, both the organization and method of operation of theinvention, in general, together with further objectives and advantagesthereof, may be more easily understood by reference to the drawings andthe following description. The drawings are not intended to limit thescope of this invention, which is set forth with particularity in theclaims as appended hereto or as subsequently amended, but merely toclarify and exemplify the invention.

FIG. 1A depicts a human foot afflicted with hammertoe deformity;

FIG. 1B depicts a human hand afflicted with mallet finger deformity.

FIG. 2 is a perspective view of an intramedullary fixation implant ofthe present invention inserted into the bones of patient's footaccording to the preferred embodiment of the invention;

FIG. 3A is a perspective view of the intramedullary fixation implant ofthe present invention according to the preferred embodiment of theinvention;

FIG. 3B is a front view of the intramedullary fixation implant shown inFIG. 3A according to the preferred embodiment of the invention;

FIG. 3C is a side view of the intramedullary fixation implant shown inFIG. 3A according to the preferred embodiment of the invention;

FIG. 3D is a top view of the intramedullary fixation implant shown inFIG. 3A according to the preferred embodiment of the invention;

FIG. 3E is a bottom view of the intramedullary fixation implant shown inFIG. 3A according to the preferred embodiment of the invention;

FIG. 3F is a side view of the intramedullary fixation implant shown inFIG. 3A in a collapsed position according to the preferred embodiment ofthe invention;

FIG. 4 is a cross-sectional view of the intramedullary fixation implantshown in FIGS. 3A-3E according to the preferred embodiment of theinvention;

FIG. 5A is a perspective view of an implant driving tool according tothe preferred embodiment of the invention;

FIG. 5B is a side view of the implant driving tool shown in FIG. 5Aaccording to the preferred embodiment of the invention;

FIG. 5C is a front view of the implant driving tool shown in FIG. 5Aaccording to the preferred embodiment of the invention;

FIG. 6A is a cross-sectional view of the implant driving tool shown inFIGS. 5A-5C according to the preferred embodiment of the invention;

FIG. 6B is an enlarged cross-sectional view of the implant driving toolshown in FIGS. 5A-5C used with the intramedullary fixation implant shownin FIGS. 3A-3E according to the preferred embodiment of the invention;

FIG. 7 is a flow chart depicting illustrative steps of an embodiment ofthe invention; and

FIGS. 8A-8P depict details of certain steps of FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

The invention may be understood more readily by reference to thefollowing detailed description of a preferred embodiment of theinvention. However, techniques, systems, and operating structures inaccordance with the invention may be embodied in a wide variety of formsand modes, some of which may be quite different from those in thedisclosed embodiment. Consequently, the specific structural andfunctional details disclosed herein are merely representative, yet inthat regard, they are deemed to afford the best embodiment for purposesof disclosure and to provide a basis for the claims herein, which definethe scope of the invention. It must be noted that, as used in thespecification and the appended claims, the singular forms “a”, “an”, and“the” include plural referents unless the context clearly indicatesotherwise.

The intramedullary fixation implant of present invention is describedwith reference to the treatment of a hammertoe deformity illustrated inFIG. 1A. However, it should be appreciated that the present inventionmay be used to treat any other digital deformities, including, but notlimited to claw toes, mallet toes, bone spurs, overlapping andunderlapping toes, mallet fingers, jersey fingers, coach's fingers, andthe like. As such, the present invention may be utilized for thefixation of the following bones in the foot shown in FIG. 1A: distalphalanx 101 to the middle phalanx 103 in the distal interphalangealjoint 104, middle phalanx 103 to the proximal phalanx 105 in theproximal interphalangeal joint 106, or the proximal phalanx 105 to themetatarsal 107 in the metatarsophalangeal joint 108. Similarly, thepresent invention may be utilized for the fixation of the followingbones in the hand shown in FIG. 1B: distal phalanx 111 to the middlephalanx 113 in the distal interphalangeal joint 114, middle phalanx 113to the proximal phalanx 115 in the proximal interphalangeal joint 116,or proximal phalanx 115 to the metacarpal 117 in the metacarpophalangealjoint 118.

Referring now to FIG. 2, there is shown an intramedullary fixationimplant 200 that may be used in the practice of the present invention.As shown in FIG. 2, intramedullary fixation implant 200 may be used tojoin the middle phalanx 103 to the proximal phalanx 105 in the proximalinterphalangeal joint 106 of foot 100. Intramedullary fixation implant200 is used to translate compression between the middle phalanx 103 andthe proximal phalanx 105 as will be further apparent below.Intramedullary fixation implant 200 may be made of PEEK(polyetheretherketone) material. The intramedullary fixation implant 200is preferably made of radiolucent material, allowing for clearvisualization of the fusion site. In other embodiments, intramedullaryfixation implant 200 may be made of other materials known in the art,including other PAEK (polyaryletherketone) plastics, SST, titanium,NiTi, Cobalt chrome, polylactic acid, or other similar types ofmaterials. Also, intramedullary fixation implant 200 may be coated withan osteoconductive material, such as, for example, plasma spray or othersimilar types of porous materials, that are capable of supporting orencouraging bone ingrowth into the material.

Intramedullary fixation implant 200 is shown in greater detail in FIGS.3A-3E, where FIG. 3A is a perspective view of the intramedullaryfixation implant 200, FIG. 3B is a front view thereof, FIG. 3C is a sideview thereof, FIG. 3D is a top view thereof, and FIG. 3E is a bottomview thereof. As shown, intramedullary fixation implant 200 preferablycomprises unitary elongated body 201 extending from a first end 211 to asecond end 212 along longitudinal axis 210. Intramedullary fixationimplant 200 further comprises a first fixation portion 202 at the firstend 211 and a second fixation portion 204 at the second end 212connected via middle portion 206.

The first fixation portion 202 of intramedullary fixation implant 200 issubstantially cylindrical in shape. Alternatively, first fixationportion 202 may comprise a taper, with width that decreases from themiddle portion 206 to the first end 211 (not shown). First fixationportion 202 preferably comprises on its exterior surface 216 threads215. Threads 215 are preferably helical dual-lead threads. Firstfixation portion 202 may also be provided with a self-tapping leadingedge 213 to provide portion 202 with the ability to remove bone materialduring insertion of the first fixation portion 202 into the bone.

The middle portion 206 is substantially cylindrical in shape orcross-section. However, the middle portion may comprise other shapes orcross-sections—it may have rectangular, square, or hexagonal shape orcross-section.

The second fixation portion 204 preferably comprises a first projection231 and a second projection 232 extending from the middle portion 206 tothe second end 212. Although two projections are illustrated, secondfixation portion 204 may comprise three or four projections. FIG. 4 isthe cross-sectional view of intramedullary fixation implant 200 takenalong line 4-4 in FIG. 3D. As shown in FIG. 3B, and in further detail inFIG. 4, the first and second projections 231 and 232 further compriseoppositely-disposed outer-facing convex surfaces 237 and 238. In apreferred embodiment, outer facing convex surfaces 237 and 238 aresubstantially parallel to one another. Further, the first and secondprojections 231 and 232 preferably comprise oppositely-disposedinner-facing flat surfaces 235 and 236, longitudinally separated by aV-shaped slot 243. The oppositely-disposed inner-facing flat surfaces235 and 236 are offset from the longitudinal axis 210 by angle A. AngleA is preferably in the range of about 0 degrees to about 45 degrees,more preferably from about 5 degrees to about 30 degrees, and morepreferably it is about 10 degrees. Projections 231 and 232 are flexiblesuch that they can be collapsed from a normal or open position shown inFIG. 4 to a collapsed position shown in FIG. 3F, where projections 231and 232 are brought toward each other. In a collapsed position,inner-facing flat surfaces 235 and 236 are preferably substantiallyparallel to each other and to the longitudinal axis 210. As show in FIG.4, second fixation portion 204 further comprises a circular compressionnotch 234 formed at the meeting-place of the first and secondprojections 231 and 232 at the inner-facing flat surfaces 235 and 236.Circular compression notch 234 assists in allowing projections 231 and232 to compress towards each other.

The first and second projections 231 and 232 further comprise aplurality of barbs 241 and 242, respectively. In a preferred embodiment,first and second projections 231 and 232 each comprise five barbs 241and 242, respectively. Barbs 241 and 242 extend outwardly from theouter-facing convex surfaces 237 and 238 of first and second projections231 and 232, respectively, away from the longitudinal axis 210. Barbs241 of the first projection 231 and barbs 242 of the second projection232 are shaped and arranged along the outer-facing surfaces 237 and 238,respectively, such that they coextensively or cooperatively form ahelical thread 250 along the second fixation portion 204. As a result,barbs 241 of the first projection 231 and the barbs 242 of the secondprojection 232 are asymmetrically disposed. In the preferred embodiment,the helical thread 250 comprises a reverse-buttress thread that causesthe second fixation portion 204 to be better secured to a bone againstthe force of deflection. The helical thread 250 formed by barbs 241 and242 is used to translate compression between two bones, such as themiddle phalanx 103 and proximal phalanx 105, by applying torque to theintramedullary fixation implant 200 as will be later described.

As shown in FIG. 4, the elongated body 201 comprises length L. In apreferred embodiment, length L is in the range of approximately 13.5millimeters (mm) to approximately 15 mm. First fixation portion 202comprises length L1 and major diameter 1d, while second fixation portion204 comprises length L2 and major diameter 2d. In a preferredembodiment, length L1 is in the range of approximately 6.5 mm toapproximately 7.0 mm, length L2 is in the range of approximately 5.5 mmto approximately 6.8 mm, major diameter 1d is in the range ofapproximately 2.8 mm to approximately 4.0 mm, and major diameter 2d isin the range of approximately 4.0 mm to approximately 5.5 mm. The sizeand length of the intramedullary fixation implant 200 that may be usedin the practice of the invention can vary considerably depending on thesize of the bones that are being joined and the surgeon's preferences.Intramedullary fixation implant 200 is cannulated along length L havinga bore 221 aligned along longitudinal axis 210 and extending from firstend 211 to second end 212. Bore 221 comprises diameter D provided tointeract with a guide wire or a Kirschner wire (K-wire) by receiving theK-wire within the bore 221 as will be later described. Preferably,diameter D is constant throughout length L of intramedullary fixationimplant 200 when projections 231 and 231 are in a normal or openposition. Different diameters and K-wire sizes may be used depending onthe diameter of the bones that are being joined and the surgeon'spreferences. Illustratively, the diameter of the K-wire is in the rangeof approximately 0.7 mm to approximately 4.0 mm, and more preferablyapproximately 0.9 mm to approximately 1.6 mm. In a preferred embodiment,intramedullary fixation implant 200 comprises various sizes toaccommodate variations in bone sizes. For example, the intramedullaryfixation implant 200 may be available in the following three sizes anddimensions:

TABLE 1 Size Small Medium Large Overall length L (mm) 13.5 15 15 Firstfixation portion 6.5 7.0 7.0 length L1 Second fixation portion 5.5 6.86.8 length L2 Major diameter 1d (mm) 2.8 3.4 4.0 Major diameter 2d (mm)4.0 4.5 5.5 Guide wire (mm) 1.1 1.4 1.6 compatibility

The first fixation portion 202 and second fixation portion 204, shown inFIG. 3C, are disposed along longitudinal axis 210. In alternativeembodiment, second fixation portion 204 may be offset from thelongitudinal axis 210 and from the first fixation portion 202 at anangle (not shown). Such an angle will determine the angle of the bonefixation. Preferably, the second fixation portion 204 may be offset fromthe longitudinal axis 210 at an angle between about 0 degrees and about30 degrees, and more preferably between about 5 degrees and about 10degrees. During operation, a surgeon may select an intramedullaryfixation implant 200 having a desired angle to adopt the intramedullaryfixation implant 200 to the implantation site.

As shown in FIGS. 3B and 3D, each barb 241 and 242 further comprisesopposing flat side walls 244 and 245, respectively. As a result, thesecond fixation portion 204 comprises a cross section having oppositelydisposed convex edges 301 and oppositely disposed flat edges 302.Opposing flat side walls 244 and 245, and thereby oppositely disposedflat edges 302, are provided to engage with an implant driving tool asdescribed below.

FIGS. 5A-5C illustrate a preferred embodiment of an implant driving tool500 used to drive the intramedullary fixation implant 200 into the boneof fixation. FIG. 5A illustrates the prospective view of the implantdriving tool, FIG. 5B illustrates a side view thereof, and FIG. 5Cillustrates the front view thereof. FIG. 6A illustrate the cross sectionof the implant driving tool taken along line 6-6 in FIG. 5C. Implantdriving tool 500 comprises an elongated body 505 extending from a firstend 511 to a second end 512 along a longitudinal axis 510. The implantdriving tool 500 further comprises a handle portion 501 disposed betweenan implant receiving portion 502 at the first end 511 and an end portion503 at the second end. Handle portion 501 may be ribbed (not shown) ormay comprise friction resistant material to assist the surgeon tomanually apply torque to the implant driving tool 500. Alternatively, orin addition, end portion 503 may be sized to receive a torquetransmitting tool (not show). As shown in FIG. 6A, implant driving tool500 is cannulated having a bore 508 extending along longitudinal axis510 of elongated body 505.

Implant receiving portion 502 preferably comprises an aperture 504 atthe first end 511 of the implant driving tool 500. Aperture 504 extendsfrom an open end 513 at the first end 511 of the implant driving tool500 to an inner base wall 506. In a preferred embodiment, aperture 504is sized for receiving the second fixation portion 204 of intramedullaryfixation implant 200 in a normal or open position as shown in FIG. 6B.Aperture 504 comprises a cross section that complements the crosssection of the second fixation portion 204. As shown in FIGS. 5A and 5C,aperture 504 comprises oppositely disposed inner flat side walls 507 andoppositely disposed inner concave side walls 509. When the secondfixation portion 204 of the intramedullary fixation implant 200 isinserted into aperture 504, as shown in FIG. 6B, second fixation portion204 is aligned with aperture 504 such that oppositely disposed convexedges 301 are disposed against the concave side walls 509 of aperture504, and the oppositely disposed flat edges 302 are disposed against theoppositely disposed flat side walls 507 (not shown). Aperture 504further comprises depth P sufficient to receive the second fixationportion 204. The inner base wall 506 prevents the intramedullaryfixation implant 200 from overinsertion into aperture 504 of implantdriving tool 500. When the second fixation portion 204 is inserted intoaperture 504, the second end 212 of the intramedullary fixation implant200 abuts the inner base wall 506 of aperture 504. In a preferredembodiment, aperture 504 comprises depth P equal to the length of thesecond fixation portion 204 plus the length of the middle portion 206 ofthe intramedullary fixation implant 200 such that the first fixationportion 202 is not inhibited by aperture 504 when the second fixationportion 204 is fully inserted into aperture 504 of the implant drivingtool 500. Implant receiving portion 502 of the implant driving tool 500may further comprise a pair of indicators 514, such as arrows, onopposite sides of its outer surface, parallel to the oppositely disposedinner flat side walls 507. Indicators 514 are used to align theintramedullary fixation implant 200 with the bones as will be laterdescribed.

The intramedullary fixation implant 200 of the present invention isutilized to join two bones together, such as a first bone and a secondbone, and to translate compression between the bones. FIGS. 7 and 8A-8Sdepict illustrative operative technique of an embodiment of theinvention used to treat hammertoe deformity between the proximal phalanx105 (i.e., a first bone) and the middle phalanx 103 (i.e., a secondbone) in the proximal interphalangeal joint 106. It will be understoodthat the operative technique is only illustrative, that the order ofexecution of some steps may vary, and that some steps may not need to beused in the treatment of a particular patient in accordance with theinvention.

As shown in FIG. 8A, before beginning the operative procedure, anintra-operative template 800 may be used to determine the optimalimplant size. This template 800 is radiopaque and can be used withfluoroscopy. Template 800 may comprise a plurality of rectangularextensions 803 each corresponding to a differently sized intramedullaryfixation implant 200. In this example, three rectangular extensions 803are used corresponding to a small, medium, and large sizedintramedullary fixation implant 200. The length and width of eachrectangular extension 803 correspond to the length and major diameter ofthe threaded end of the implant for the middle phalanx 103. Eachrectangular extension 803 is aligned with the middle phalanx 103 by thesurgeon to determine the optimal implant size.

After a proper implant size is chosen, in step 710 an incision is madein the foot over the dorsal aspect of the proximal interphalangeal joint106, while soft tissue is released as necessary, so as to provide acomplete visualization of the articular surfaces of the middle andproximal phalanges. The incision may be a dorsal longitudinal incisionor a two semi-elliptical incision. As shown in FIG. 8B, the distalaspect or face 125 of the proximal phalanx 105 and the proximal aspector face 123 of the middle phalanx 103 are excised in step 712 usingblade 802 of cutting tool 801. In a preferred embodiment, the distalaspect of the proximal phalanx 105 is resected just posterior to thehead of the phalange as either a straight cut (FIG. 8C), or at an angle804 (FIG. 8D). Such an angle 804 will determine the angle of the bonefixation. Preferably, angle 804 is in a range of between about 0 degreesand about 30 degrees, and more preferably between about 5 degrees andabout 10 degrees. In a preferred embodiment, angle 804 is approximately10 degrees. The articular cartilage of the middle phalanx 103 may bedenuded. In an alternative embodiment, the middle phalanx 103 can bealso resected.

In step 714, a retrograde K-wire 805 is advanced into the proximalphalanx 105 along its central axis as shown in FIG. 8E, approximately 10mm in depth. The K-wire 805 is advanced by the surgeon in a direction ofthe desired alignment of the intramedullary fixation implant 200 withrespect to the proximal phalanx 105. As shown in FIG. 8F, If theproximal phalanx 105 was resected at an angle 804, the guide wire 805 isplaced perpendicular to the resection of the proximal phalanx 105. Thenin step 716, as shown in FIG. 8G, the proximal phalanx 105 is drilledusing drill bit 808 over the K-wire 805 to create a hole 807 in theproximal phalanx 105. The K-wire 805 is used to guide drill bit 808 intothe desired alignment. Accordingly, the drill bit 808 used in thepresent invention is preferably cannulated such that it may fit over theK-wire 805. The drill bit 808 may be driven manually or via a torquetransmitting tool (not shown). The drill bit 808 may comprise apre-marked depth line marking 809 to indicate how deep to advance thedrill bit 808 into the proximal phalanx 105. The K-wire 805 is thenremoved from the proximal phalanx 105.

In step 718, as shown in FIG. 8H the K-wire 805 is advanced into themiddle phalanx 103, through the distal phalanx 101, until the K-wire 805exits the toe. In a preferred embodiment, the K-wire 805 is advancedinto the middle phalanx 103 until a minimum of approximately 10 mm ofK-wire 805 extends out of the middle phalanx 103. The same K-wire 805may be used that was previously used in FIGS. 8E-8G. Alternatively, thesurgeon can use a different K-wire. The K-wire 805 is advanced by thesurgeon in a direction of the desired alignment of the intramedullaryfixation implant 200 with respect to the middle phalanx 103. In step720, as shown in FIG. 8I, the middle phalanx 103 is tapped over theK-wire 805 to create a threaded hole 815 in the middle phalanx 103 usingtap 810 driven either manually or by a torque transmitting tool (notshown). The K-wire 805 is used to guide tap 810 into the desiredalignment. Accordingly, tap 810 used in the present invention ispreferably cannulated such that is may fit over the K-wire 805. Threadedhole 815 comprises threads that correspond to threads 215 of the firstfixation portion 202. Guide tap 810 may comprise a depth line marking811 to indicate how deep to advance the guide tap 810 into the middlephalanx 103.

Next, in step 722, the second fixation portion 204 of intramedullaryfixation member 200 is inserted into aperture 504 of the implant drivingtool 500 as shown in FIG. 6B. As shown in FIG. 8J, in step 724, thefirst fixation portion 202 is rotatably advanced into the threaded hole815 in the middle phalanx 103 over the K-wire 805 using the implantdriving tool 500. As such, the K-wire 805 is advanced into bore 221 ofthe intramedullary fixation implant 200. The diameter of K-wire 805 thatmay be used in the practice of the present invention preferably isadapted to fit within diameter D of bore 221 of intramedullary fixationimplant 200. The first fixation portion 202 may be advanced manuallyinto the threaded hole 815 by rotating the handle 501 of the implantdriving tool 500 or by attaching a torque transmitting tool to endportion 503 of the implant driving tool 500 (not shown). Threads 215engage the threads tapped into the threaded hole 815. In an alternativeembodiment, the middle phalanx 103 is not pre-tapped. It may be onlypre-drilled or the intramedullary fixation implant 200 may be advancedinto the middle phalanx 103 using the self-tapping leading edge 213. Thefirst fixation portion 202 is rotatably advanced into the threaded hole815 in the middle phalanx 103 until the first end 511 of the implantdriving tool 500 meets the middle phalanx 103. This will ensure that thefirst fixation portion 202 is within the middle phalanx 103, leaving theunthreaded middle portion 206 (FIG. 6B) of the implant at thebone-to-bone interface. After the first fixation portion 202 is fullyinserted into the middle phalanx 103 as desired, as shown in FIG. 8K,the implant driving tool 500 is oriented so that an indicator 514 of theimplant driving tool 500 is aligned with the dorsal aspect of the middlephalanx 103 (12 o'clock position). This ensures the proper orientationof the implant in the phalanx. Then, the implant driving tool 500 isremoved from the second fixation portion 204.

As shown in FIG. 8L, the K-wire 805 is pulled further into middlephalanx 103 until it is housed within the first fixation portion 202 anddoes not extend past the middle portion 206 of intramedullary fixationimplant 200. In step 726, the first and second projections 231 and 232of second fixation portion 204 are collapsed in directions D2 and D3 toa collapsed position shown in FIG. 3F. The first and second projections231 and 232 may be collapsed by being compressed with forceps 812.

In a preferred embodiment, as shown in FIG. 8N, the middle phalanx 103is counter-rotated in direction D1 in step 728. Preferably, the angle ofrotation is in the range of about 0 degrees to about 90 degrees, morepreferably about 10 degrees to about 80 degrees, and more preferably itis about 60 degrees. Next, in step 730, the second fixation portion 204is pressed linearly into hole 807 in the proximal phalanx 105 indirection D4 lateral to the proximal phalanx 105 and hole 807. The jointis firmly compressed until the implant is completely buried and thesurfaces of the resectioned joint are fully opposed as shown in FIG. 8O.Because no pressure is provided to the first and second projections 231and 232 of second fixation portion 204 by the forceps, first and secondprojections 231 and 232 will deploy to substantially normal or openposition as shown in FIGS. 3A-3B.

As shown in FIG. 8O, in step 732, the middle phalanx 103 is rotated tothe final and desired fixation position in direction D5, thereby furtheradvancing second fixation portion 204 into the proximal phalanx 105 viathe help of the helical thread 250 formed on the second fixation portion204. Preferably the angle of rotation is in the range of about 0 degreesto about 90 degrees, more preferably about 10 degrees to about 80degrees, and more preferably it is about 60 degrees. The rotation indirection D5 adds further compression in directions D6 and D7 betweenmiddle phalanx 103 and proximal phalanx 105. Generally, the opposingthreads of the second fixation portion 204 allow for approximately anadditional 0.25 mm of compression for every 30 degree ofcounter-rotation. In a preferred embodiment, an angle of rotation ofabout 60 degrees adds about 0.5 mm compression in directions D6 and D7.

In a preferred embodiment, in step 734, as shown in FIG. 8P, the K-wire805 is advanced in direction D4 through bore 221 in between first andsecond projections 231 and 232 to further deploy first and secondprojections 231 and 232 outwardly into an open position in the proximalphalanx 105. After the procedure, the guide wire 805 can then beremoved. In an alternative embodiment, as shown in FIG. 8P, the guidewire 805 can be driven proximally into the metatarsal 107 to stabilizethe metatarsophalangeal joint 108. The guide wire 805 may be left inplace for the initial recovery period to allow the soft tissue to healand prevent metatarsophalangeal joint 108 subluxation. After the initialrecovery, the guide wire 805 can be removed.

As will be apparent to those skilled in the art, numerous variations maybe practiced within the spirit and scope of the present invention. Forexample, a variety of different tools—screw drivers, wrenches, reductioninstruments and drill guides—may be used in the practice of theinvention. Implants of different sizes and different shapes may be used.Likewise different thread sizes and configurations may be used. Theremay also be variation in the procedure used to implant theintramedullary fixation implant in the bones. Certain steps can beomitted or combined with other steps and certain steps can be performedin a different order. For example, in some procedures it may not benecessary to excise the bone faces, use a K-wire, or pre-drill orpre-tap holes in the bones.

While the invention has been described with reference to the preferredembodiment and alternative embodiments, which embodiments have been setforth in considerable detail for the purposes of making a completedisclosure of the invention, such embodiments are merely exemplary andare not intended to be limiting or represent an exhaustive enumerationof all aspects of the invention. The scope of the invention, therefore,shall be defined solely by the following claims. Further, it will beapparent to those of skill in the art that numerous changes may be madein such details without departing from the spirit and the principles ofthe invention. It should be appreciated that the invention is capable ofbeing embodied in other forms without departing from its essentialcharacteristics.

What is claimed is:
 1. An intramedullary fixation implant comprising: anelongated body extending from a first end to a second end; a firstfixation portion at the first end; and a second fixation portion at thesecond end comprising a first projection and a second projectionlongitudinally separated by a slot, wherein the first projection and thesecond projection comprise a plurality of barbs extending outwardly fromoppositely-disposed outer-facing surfaces of the first and secondprojections.
 2. The intramedullary fixation implant of claim 1, whereinsaid plurality of barbs are shaped and arranged along the outer-facingsurfaces of the first and second projections such that theycooperatively form a thread along the second fixation portion.
 3. Theintramedullary fixation implant of claim 1, wherein the elongated bodycomprises material selected from the group consisting of PEEK, PAEK,SST, titanium, NiTi, Cobalt chrome, polylactic acid, osteoconductivematerial, and a combination thereof.
 4. The intramedullary fixationimplant of claim 1, wherein the first fixation portion is substantiallycylindrical in shape.
 5. The intramedullary fixation implant of claim 1further comprising a middle portion disposed between the first fixationportion and the second fixation portion.
 6. The intramedullary fixationimplant of claim 5, wherein the middle portion comprises a cross sectionselected from the group consisting of a cylinder, a rectangle, a square,and a hexagon.
 7. The intramedullary fixation implant of claim 5,wherein the first fixation portion is tapered with width that decreasesfrom the middle portion to the first end of the elongated body.
 8. Theintramedullary fixation implant of claim 1, wherein the first fixationportion comprises threads on its exterior surface.
 9. The intramedullaryfixation implant of claim 8, wherein the threads are helical dual-leadthreads.
 10. The intramedullary fixation implant of claim 1, wherein thefirst fixation portion comprises a self-tapping leading edge forremoving bone material during insertion of the first fixation portioninto a bone.
 11. The intramedullary fixation implant of claim 1, whereinthe first projection and the second projection are flexible such thatthey can be collapsed from an open position to a collapsed position. 12.The intramedullary fixation implant of claim 1, wherein the outer-facingsurfaces of the first and second projections are convex.
 13. Theintramedullary fixation implant of claim 1, wherein outer-facingsurfaces are substantially parallel.
 14. The intramedullary fixationimplant of claim 1, wherein the slot is V-shaped.
 15. The intramedullaryfixation implant of claim 1, wherein the first projection and the secondprojection comprise oppositely-disposed inner-facing flat surfacesseparated by the slot.
 16. The intramedullary fixation implant of claim15, wherein the first projection and the second projection arecollapsible, wherein when the first projection and the second projectionare in a collapsed position the inner-facing flat surfaces aresubstantially parallel.
 17. The intramedullary fixation implant of claim15, wherein the second fixation portion extends along a longitudinalaxis and wherein the inner-facing flat surfaces are offset from thelongitudinal axis by an angle.
 18. The intramedullary fixation implantof claim 17, wherein the angle is in the range of about 0 degrees toabout 45 degrees.
 19. The intramedullary fixation implant of claim 17,wherein the angle is in the range of about 5 degrees to about 30degrees.
 20. The intramedullary fixation implant of claim 17, whereinthe angle is about 10 degrees.
 21. The intramedullary fixation implantof claim 1, wherein the elongated body comprises a circular compressionnotch formed at the meeting-place of the first projection and the secondprojection to assist in collapsing the first projection and secondprojection towards each other.
 22. The intramedullary fixation implantof claim 2, wherein the thread formed by the plurality of barbs alongthe second fixation portion comprises a reverse-buttress helical thread.23. The intramedullary fixation implant of claim 2, wherein the threadformed by the plurality of barbs along the second fixation portiontranslates compression between a first bone and a second bone when theintramedullary fixation implant is implanted between the first andsecond bones.
 24. The intramedullary fixation implant of claim 1,wherein the elongated body is cannulated.
 25. The intramedullaryfixation implant of claim 1, wherein the elongated body comprises a boreextending from the first end to the second end.
 26. The intramedullaryfixation implant of claim 25, wherein the bore receives a guide wire.27. The intramedullary fixation implant of claim 26, wherein the guidewire is used to deploy the first and second projections into an openposition during implantation of the intramedullary fixation implant. 28.The intramedullary fixation implant of claim 1, wherein each barb of theplurality of barbs comprises opposing outer-facing flat side walls. 29.The intramedullary fixation implant of claim 28, wherein the opposingouter-facing flat side walls of each barb of the plurality of barbs areformed to cooperate with an implant driving tool.
 30. The intramedullaryfixation implant of claim 29, wherein the implant driving tool comprisesan elongated body extending from a first end to a second end along alongitudinal axis, and an aperture at the first end of the elongatedbody of the implant driving tool, wherein said aperture is sized forreceiving the second fixation portion of the intramedullary fixationimplant.
 31. The intramedullary fixation implant of claim 30, whereinthe implant driving tool comprises a handle portion used fortransmitting torque to the implant driving tool.
 32. The intramedullaryfixation implant of claim 30, wherein the implant driving tool furthercomprises an end portion at the second end of the elongated body of theimplant driving tool, wherein the end portion is sized for receiving atorque transmitting tool.
 33. The intramedullary fixation implant ofclaim 29, wherein the implant driving tool is provided for driving thefirst fixation portion of the intramedullary fixation implant into abone.
 34. The intramedullary fixation implant of claim 30, wherein theaperture of the implant driving tool comprises an inner base wall forpreventing the second fixation portion from being overinserted into theaperture of the implant driving tool.
 35. The intramedullary fixationimplant of claim 1, wherein the second fixation portion is offset fromthe first fixation portion at an angle.
 36. The intramedullary fixationimplant of claim 35, wherein the angle is in the range of about 0degrees to about 30 degrees.
 37. The intramedullary fixation implant ofclaim 35, wherein the angle is in the range of about 5 degrees to about10 degrees.
 38. The intramedullary fixation implant of claim 35, whereinthe angle defines the angle of the bone fixation.
 39. An intramedullaryfixation implant comprising: a first fixation portion; and a secondfixation portion connected to the first fixation portion; wherein thesecond fixation portion comprises a first projection and a secondprojection separated by a slot, wherein the first projection and thesecond projection comprise a plurality of barbs shaped and arrangedalong the first and second projections such that they cooperatively forma thread along the second fixation portion.